The present invention relates to apparatus and methods for preparing the reinforcing steel for precast or cast in place reinforced concrete structures and shapes, although the present invention is not intended to be limited only to concrete structures. Representative examples of precast concrete structures are concrete pipes, boxes, tanks, containers, building structures and rooms, i.e., apartment and motel rooms as well as jail cells and basements. In order to simplify the description, reinforced precast concrete box pipe will be used as the concrete shape being manufactured in view of its similarity to many of the straight-sided structures.
In the usual method of manufacturing precast concrete box pipe, reinforcing mats produced from welded wire fabric or Rebar (rod) are joined together to make reinforcing cages to be used as the reinforcement structure for the precast concrete box pipes. Little care has been taken in the cutting, bending and positioning of the rod or wire fabric mats used in making the reinforcing cages. When wire fabric mats are used, it is difficult to bend the fabric at a right angle at the precise distance from the ends of the fabric mat to position the primary reinforcing steel at its designated location in the top or bottom slabs of the concrete box pipe. This is difficult because the wires perpendicular to the primary reinforcing wires are not positioned to yield precise location of the bend. Also, when multiple layers of reinforcing cages are used, the positioning and separation of these cages are not carefully controlled. The cages produced from the mats are allowed to bow inwardly and outwardly within the surface boundaries of the concrete pipe which makes their spacing relative to the surfaces of the concrete structure difficult to maintain. The assumption is usually made that when the concrete is poured, any mistakes will be covered and the concrete structure is strong enough anyway so that it really does not make a difference if the reinforcing is precisely located.
The overall result of all of the above thinking is inconsistent spacing of the reinforcing within the pipe structure and sections of box pipe are cast with varying strengths and load bearing abilities.